Apparatus and method for oil sand exploitation

ABSTRACT

A downhole apparatus for oil sand exploitation, including at least a casing for housing a water conduit for receiving water, at least one steam generation chamber being in fluid communication with said water conduit and having at least one steam outlet, at least one electrical heater, being thermally connected to said steam generation chamber, at least one crude oil conduit for recovering crude oil. A method including injecting steam from at least one steam generation chamber coupled to an oil recovery conduit into a reserve; and removing oil from the reserve through the conduit, wherein the least one steam generation chamber is disposed on the oil recovery conduit, and the steam generation chamber includes a plurality of heating conduits each including a heating element and a thermally conductive material therein, and at least one reservoir surrounding the plurality of heating conduits from which the steam is produced.

CROSS-REFERENCE TO RELATED APPLICATION

The application claims the benefit of the earlier filing date of co-pending European Patent Application No. 12150055.7, filed Jan. 3, 2012, and incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to a method and an apparatus for in situ mobilizing of heavy oil or crude oil by steam injection.

DESCRIPTION OF THE RELATED ART

Oil sand, as well referred to as tar sand comprises sand grains coated with tar like petroleum crude oil, briefly referred to as crude oil. The crude oil in the oil sand has a high viscosity and must be heated or diluted to flow. In-situ exploitation of oil sands can be accomplished by “steam assisted gravity drainage”, abbreviated as SAGD. SAGD uses a horizontally extending steam injection well forming a steam generation chamber for mobilizing the crude oil in the oil sand. The mobilized crude oil pours downward and is recovered by a second horizontally extending well, as so called production well, as disclosed in U.S. Patent Publication No. 2001/0278001A1.

The steam can be either produced by above ground facilities or downhole by an electrical heater as suggested by U.S. Pat. No. 4,805,698. The water is supplied from above ground by a water supply line. The electrical steam generator heats the water to generate steam. The steam is injected into the sand and mobilizes the crude oil, which is collected by adjacent production wells.

SUMMARY OF THE INVENTION

The problem to be solved by the invention is to improve in-situ oil sand exploitation.

Solutions of the problem are provided by a downhole apparatus and a method for exploitation of an oil sand reservoir as described by the respective independent claims. The dependent claims relate to further improvements of the invention.

The downhole apparatus for oil sand exploitation, comprises a least a casing which houses a water conduit for receiving water via a water pipe and at least one steam generation chamber being in fluid communication with said water conduit and having at least one steam outlet. The steam generation chamber is thermally connected to an electrical heater. The downhole apparatus further comprises at least one crude oil conduit for recovering crude oil, which has been mobilized by said steam. Such downhole apparatus permits to inject steam for mobilization of the crude oil into the oil sand and to recover the crude oil by a single apparatus, and thus requires only a single bore.

The casing may preferably house the at least one crude oil conduit. The casing may for example be or include a multiple conduit tube, wherein the at least one water conduit and the at least one crude oil conduit are each at least one of the multiple conduits. This permits a stable design of the housing.

The at least one steam generation chamber is preferably supported by the peripheral surface of the casing. This position of the steam generation chamber permits a simple injection of the steam generated in said steam generation chamber into the oil sand.

Preferably there are multiple, e.g. five or nine, at least two steam generation chambers arranged around the peripheral surface of the casing defining a bundle of steam generation chambers. In one embodiment, there is one bundle of steam generation chambers. In another embodiment, there are two or more bundles arranged at different positions along a distal length of the casing. The one or more bundles of steam generation chambers permit homogeneous injection of steam and thus an efficient exploitation of the oils sand. Because the one or more bundles of steam generation chambers are arranged around the casing, the one or more bundles also act to maintain or raise a temperature of the casing which aids in removal of crude oil from a reservoir (via the crude oil conduit in the casing).

Each steam generation chamber preferably has a cladding compartment surrounding a heater tube. The heater tube may house at least one electrical heater cartridge. This permits on the one hand to efficiently heat the water and on the other hand a simple replacement of the electrical heater cartridge in case of failure. The heater tube preferably houses at least one spare electrical heater cartridge. This permits longer operating intervals between retracting the downhole apparatus.

The heater tube may be hollow and may have an interior containing a composition of inorganic compounds and possibly pure elemental species. Examples for such a composition are described in U.S. Pat. Nos. 6,132,823; 6,911,231; 6,916,430; 6,811,720 and U.S. Patent Publication No. 2005/0056807, which are incorporated by reference as if fully disclosed herein. Such composition acts as a thermally conductive material or medium to provide at least an almost perfect homogenous distribution by the heater tube of the heat provided by the heater cartridge. The heater tube may as well be evacuated as suggested in the above references.

The heater tube may extend over the steam generation chamber, e.g. extend axially. Thus, at least one section of the heater tube extends out of the steam generation chamber into the bore. The heater tube thus reheats steam or water that cooled in a reservoir after its injection and enhances the efficiency of the exploitation.

The method for exploitation of an oil sand reservoir comprises at least the steps of producing steam in a steam generation chamber of a downhole apparatus, injecting said steam via steam outlets into the oil sand reservoir for mobilizing crude oil of the oil sand reservoir. At least part of the mobilized crude oils is recovered by said downhole apparatus. This method reduces the minimum number of bores for in situ oil sand exploitation compared to SAGD, and thus the costs.

DESCRIPTION OF DRAWINGS

In the following, the invention will be described by way of example, without limitation of the general inventive concept, on examples of embodiment with reference to the drawings.

FIG. 1 shows a schematic depiction of an oil sand exploitation system,

FIG. 2 shows a perspective view of a section of downhole apparatus,

FIG. 3 shows section of steam generation chamber.

FIG. 4 shows a schematic depiction of a second embodiment of an oil sand exploitation system.

DETAILED DESCRIPTION

The oil sand exploitation system 100 in FIG. 1 has a ground station 110 for housing the above ground facilities, like for example a controlling station 115 for monitoring and controlling the oil sand exploitation. Ground station 110 also includes a power source to, for example, provide power to an extraction well. Finally, ground station 110 includes a water source, such as a reservoir, to provide water (e.g., fresh water) to an extraction well. The ground station 110 is depicted as an onshore station, but can as well be a swimming station for exploitation of water covered oil sands.

The oil sand exploitation system 100 includes an extraction well 120 with a downhole apparatus inserted into bore 105. The downhole apparatus includes a multi conduit tube like casing 130, e.g. for a power cable 230 (see FIG. 2) for supplying power to downhole equipment, for example a protector 165, and/or a motor 153 for driving a well head and a well monitor device 140, as schematically depicted in FIG. 1. The extraction well 120 includes a steam generator 200 which may be mounted to the peripheral surface of the casing 130. The steam generator 200 is explained below in more detail with respect to FIGS. 2 and 3. The steam generator 200 is positioned in this embodiment around casing 130 at a bottom or distal portion of casing 130 a first preferably vertical section of the extraction bore 105. The steam generator 200 injects steam generally laterally into oil sand as shown in FIG. 1. The steam mobilizes crude oil in the oil sand.

Extraction well 120 is configured to collect oil (including mobilized oil in the oil sand). To this end casing 130 of the extraction well 120 includes one or more oil inlets 135 along its length that allow oil to infiltrate the casing. Disposed within casing 130 is oil conduit 125. The oil conduit 125 extends from the bottom or distal portion of casing 130 to the above ground station 110. Oil that infiltrates casing 130 enters oil conduit 125 at the conduit's distal end and is pumped to the surface and fed to a production line 109 for example by a centrifugal pump 180 being arranged in the bottom or distal portion of casing 130. Before pumping the crude oil to the above ground station 110, water may be separated from the crude oil by separator 176. Also, in the bottom or distal portion of casing 130 are an Electric Cable Clip 195, a Venting Valve 172, Single Flow Valve 185, a Power Cable 175, the Rotary Separator 176, a Protector 165, a Cable Head 162, a Motor 152 and Well Monitor Device 140. In between are a couple of water spray holes 145 to eject water or steam (e.g., when connected to steam generation unit 200 described below) and oil inlets 135.

FIG. 2 shows a section of an isometric view of casing 130 including the steam generator 200 of extraction well 120. The casing 130 is tube like and constructed of a metal material such as steel. Casing 130 and has multiple compartments or conduits around an inner periphery which may serve as water conduit 250 (for water from ground station 110 to steam generator 200), oil conduit 125 (for oil infiltrating oil inlets 135 in casing 130) or as cable conduit (for providing power to components in the casing (e.g., centrifugal pump 180, motor 152) and to heat cartridges associated with the steam generator 200).

The steam generator 200 comprises a bundle of heating members 300 (cf. FIG. 3). The heating members 300 are arranged around the peripheral surface of the casing 130 and are each connected to the casing 130 by, for example, one or more weld connections. Where it is desired to have more than one bundle associated with a well like extraction well 120, the bundles may be stacked one above the other along the casing 130. Referring to FIG. 3, each heating member 300 includes a heater conduit, illustrated as heater tube 310, and steam generation chamber 375 respectively made of and defined by a metal material such as steel.

In one embodiment, heater tube 310 has a circular cross-section and a diameter on the order of 57 millimeters and a length on the order of 3800 millimeters. The front facing (upper) side of the heater tube 310 is closed by conical cap 330, which may be weld connected to the heater tube 310. The rear facing side of the heater tube 310 is closed by an end cap 340, which may preferably be a water tight but releasable connection, e.g. a threaded connection.

Heater tube 310, conical cap 330 and end cap 340 define a volume or chamber 335. In one embodiment, the components, heater tube 310, conical cap 330 and end cap 340 may be pressure tested to withstand, for example, a 1.5 millipascal (mPa) pressure test. Further, an inside surface of heater tube 310 defining a volume of chamber 335, in one embodiment, is free of burrs or other debris or oil to provide a smooth, unvaried and clean surface.

As shown in FIG. 3, chamber 335 of heating member 300 is divided into a first portion and a second portion by cap 360 of a thermally conductive material such as a metal material (e.g., steel). In one embodiment, a heating element such as electrical heater cartridge 350 with positive and negative terminals located at a single end (a proximal end as viewed) is positioned in a first portion of chamber 335 (proximal to cap 360). Heater cartridge 350 may have a length on the order of 300 millimeters or less, such as a length on the order of 150 millimeters. In one embodiment, cap 360 divides chamber 335 at a distance from a first end to be sufficient to allow heater cartridge 350 to be disposed in a first portion of chamber 335 but minimizes any additional volume for the first portion. As shown in FIG. 3, when heater cartridge 350 is disposed in a first portion of chamber 335 terminals 355 extend into a volume of end cap 340. In one embodiment, end cap 340 includes lateral opening 365 that is, for example, a threaded opening for power connection to terminals 355. A conductor is fed through a peripheral conduit of casing 130 into lateral opening 365. Current is supplied to the conductor from an above ground power source in ground station 110.

Each steam generation chamber 375 is defined by, for example, cylindrical shell 320 a front wall 380 and a rear wall 370 connected by, for example, weld connections. The front wall 380 and the rear wall 370 each have an opening through which a heater tube 310 is disposed. The heater tube 310 extends axially through the steam generation chamber 375. The connection of the heater tube 310 and the front wall 380 and/or the rear wall 370 may be a weld connection.

In one embodiment, shell 320 has a length dimension on the order of 3,000 millimeters. Front wall 380 and rear wall 370 each have a diameter on the order of 110 millimeters. Rear wall 370 of shell 320 includes inlet 395 for a water source to be connected thereto to provide water to steam generation chamber 375. Water is provided from a water source at, for example, ground station 110 to steam generation chamber 375 by a peripheral conduit of casing 130 that is in fluid communication with inlet 395.

The electrical heater cartridge 350 is thermally connected to the heater tube 310 and electrically connected with a power line e.g. by power cable 230. The power (e.g., electrical current) line is preferably controlled by the controlling station 115 and may be ducted via a lateral opening like lateral opening 365. A gasket may be used for sealing the cable feedthrough. Inside heater tube 310 is a thermally conductive material like it is described in the U.S. Pat. Nos. 6,132,823; 6,911,231; 6,916,430; 7,220,365 and U.S. Patent Publication No. 2005/0056807.

Water inserted into the steam generation chamber 375 via a water inlet 395 may be heated by a heat generated in heater tube 310. A current supplied to electrical heater cartridge 350 generates heat in the heater tube 310. This heat is transferred to the steam generation chamber 375. Steam develops inside the steam generation chamber 375 and escapes through steam outlet 390 into the oil sand. A single flow pressure valve may be provided in the steam outlet 390. Thereby it can be avoided that foreign matter, like sand grains and the like enter the steam generation chamber 375. Further, the steam can be pressurized. As the heater tube 310 extends over the steam generation chamber part of the heat provided by the electrical heater cartridge 350 is as well transferred directly to the oil sand. This heat reduces the condensation of the steam close to the extraction well 120 and thus permits the steam to heat a bigger area around the extraction well and thus to better mobilize the crude oil. The mobilized crude oil can be collected via oil inlets 135 (see FIGS. 1 and 2), separated from water by rotary separator 176 and pumped by centrifugal pump 180 into the production line 109 a schematically represented in FIG. 1.

As described above and shown in FIGS. 2 and 3, heater tube 310 of heating member 300 includes a heat source (heater cartridge 350) and a thermally conductive material or media 355. Thermally conductive material 355 is present in the second portion of heater tube 310 an amount sufficient to transfer heat from heater cartridge 350 to the surface of heater tube 310. Suitable representative thermally conductive material is described in U.S. Pat. Nos. 6,132,823; 6,911,231; 6,916,430; 7,220,365 and U.S. Patent Publication No. 2005/0056807, which are incorporated by reference herein. In another embodiment, thermally conductive material 355 is an inorganic material that is a combination of oxides and one or more pure elemental species, particularly titanium and silicon. One such combination is provided in Table 1.

TABLE 1 sodium peroxide 2.705% disodium oxide 2.505% silicon 1.6% diboron trioxide 0.505% titanium 0.405% copper oxide 0.405% cobalt oxide 0.255% beryllium oxide 0.255% water, distilled, conductivity or of similar purity 89.256% dirhodium trioxide 1.6% trimanganese tetraoxide 0.255% strontium carbonate 0.255%

In an embodiment using the thermally conductive material described in Table 1, the material is introduced into each heater tube 310 of bundle 200 (see FIG. 1) in a representative range amount minus the water component, equivalent to 1/400,000 of the volume of a heating tube. In other words, a 2400 mm heating tube with a 20 mm inside diameter would have a volume of 3,215,360 mm and the thermally conductive material would be present in an amount of 8 mm3 by volume. Other amounts may also be suitable such as an amount ranging from 1/400,000 to 1/200,000 by volume. For those thermally conductive materials described in the referenced incorporated patent documents, other amounts of thermally conductive material may also be used. For example, U.S. Pat. No. 7,220,365 describes an inorganic thermally conductive material of cobalt oxide, boron oxide, calcium dichromate, magnesium dichromate, potassium dichromate, beryllium oxide, titanium diboride and potassium peroxide in amounts of 0.001 to 0.025 by volume.

In one embodiment, the thermally conductive material is introduced into a second portion of each heater tube 310 of tube bundle 200 (the second portion of heater tube 310 is defined by cap 360). Each tube is heated to evaporate the water component. The presence of cap 360 allows a proximal portion of chamber 335 to be accessed (to, for example, remove or replace heater cartridge 350) without disrupting the seal or the contents of the second portion of chamber 335. Without wishing to be bound by theory, it is believed that the thermally conductive material in the second portion of each heater tube 310 operates by mechanically conducting heat generated by a heating cartridge to the steam generation chamber 375 (e.g., solid particles of the thermally conductive material colliding with one another and with a wall of the heater tube). The thermally conductive material in heater tube 310 permits heat distribution through the tube and conducts the heat to steam generation chamber 375 (e.g., axially conducts heat). That heat, in turn, evaporates water added to chamber 375 and produces steam.

With 1 kW power provided by a heat source (e.g., an electrical heating rod), heater tube 310 including 1/400,000 by volume of the thermally conductive material described in Table 1 can generate on the order of 2000 kcal of heat or more on the surface (on an outer surface of outer cylinder 310).

Representatively, as described above with reference to FIG. 1, one or more tube bundles 200 of extraction well 120 may be used to generate and discharge steam into a petroleum reserve to, in the case of oil sands, provide sufficient liquidity to the crude oil in oil sands to allow its extraction through casing 130 and pumping conduit 125, and secondarily to provide thermal insulation to casing 130. In one embodiment, maintenance of an appropriate temperature is desired. In one embodiment, ideal performance attempts to maintain an appropriate target temperature of the steam discharge temperature despite possible changing condition (e.g., heating of the reserve). In such embodiment, the temperature of the steam produced in tubes of a tube bundle may be monitored and/or controlled by controller 115. For example, a processing protocol delivered to control computer 115 includes instructions for receiving temperature measurements from temperature sensors. Based on these measurements, instructions are provided in a machine-readable form to be executed by controller 115. Accordingly, controller 115 executes the instructions to increase or decrease the power output to one or more heating rods 350 to achieve a target temperature in a range f (e.g., 250° C. to 280° C.). It is appreciated that controller 115 may be increasing power to some heating cartridges 350 while at the same time decreasing power to other heating cartridges 350. Still further, controller 115 may be connected to pump 180 and other components in pumping conduit 125 and control the pump and/or other components based on program instructions to achieve a desired throughput from the well.

FIG. 4 shows an another embodiment of an oil sand exploitation system. In this embodiment, oil sand exploitation system 400 includes ground station 410 for housing the above ground facilities, like for example, a controller 415, a power source and a water source. Similar to FIG. 1, the above ground station 410 is depicted as onshore station, but can as well be a swimming station for exploitation of water covered oil sands. The system 400 includes a bore 405 into which an extraction well 420 with a downhole apparatus is inserted. In FIG. 1, the extraction well was inserted vertically or approximately vertically the entire length of the well. In FIG. 4, the extraction well 420 extends vertically through bore 405 at a ground surface of the well, but then extends laterally into the well. Otherwise, the construction and operation of extraction well 420 and system 400 is similar to the construction and operation of extraction well 120 and system 100 described with reference to FIGS. 1-3. The downhole apparatus includes casing 430 which is, for example a multi-conduit casing configured similar to casing 130 in FIG. 1, and one or more bundles of steam generators 500 configured similar to steam generators 200. FIG. 4 shows a single bundle disposed about and connected to a distal portion of casing 430. Water provided to each steam generation chamber of steam generator 500 is converted to steam by heat provided to the chamber by a heater tube containing a heater cartridge and a thermally conductive material as described above with reference to FIGS. 1-3. The steam is dispensed from steam outlets 490 of a steam generation chamber into the oil sands reservoir to mobilize oil in the oil sand. Mobilized oil infiltrates casing 430 through oil inlets 435 and is pumped to the surface of the well.

In the description above, for the purposes of explanation, numerous specific details have been set forth in order to provide a thorough understanding of the embodiments. It will be apparent however, to one skilled in the art, that one or more other embodiments may be practiced without some of these specific details. The particular embodiments described are not provided to limit the invention but to illustrate it. The scope of the invention is not to be determined by the specific examples provided above but only by the claims below. In other instances, well-known structures, devices, and operations have been shown in block diagram form or without detail in order to avoid obscuring the understanding of the description. Where considered appropriate, reference numerals or terminal portions of reference numerals have been repeated among the figures to indicate corresponding or analogous elements, which may optionally have similar characteristics.

It should also be appreciated that reference throughout this specification to “one embodiment”, “an embodiment”, “one or more embodiments”, or “different embodiments”, for example, means that a particular feature may be included in the practice of the invention. Similarly, it should be appreciated that in the description various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects may lie in less than all features of a single disclosed embodiment. Thus, the claims following the Detailed Description are hereby expressly incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment of the invention. 

1. A downhole apparatus for oil sand exploitation, comprising at least: a casing for housing a water conduit for receiving water, at least one steam generation chamber being in fluid communication with said water conduit and having at least one steam outlet, at least one electrical heater, being thermally connected to said steam generation chamber, at least one crude oil conduit for recovering crude oil.
 2. The downhole apparatus of claim 1 wherein the casing houses the at least one crude oil conduit.
 3. The downhole apparatus of claim 1, wherein the casing comprises a plurality of and the at least one water conduit and the at least one crude oil conduit are each one of the plurality of conduits.
 4. The downhole apparatus of claim 1, wherein the at least one steam generation chamber is coupled to the peripheral surface of the casing.
 5. The downhole apparatus of claim 1, wherein at least two steam generation chambers are arranged in a bundle arranged around the peripheral surface of the casing.
 6. The downhole apparatus of claim 1, wherein the steam generation chamber comprises a cladding compartment surrounding a heating conduit; and the heating conduit houses at least one electrical heating element.
 7. The downhole apparatus of claim 6, wherein the heating conduit is hollow, the apparatus further comprising a thermally conductive material disposed in the heating conduit.
 8. The downhole apparatus of claim 7, wherein the heating conduit is evacuated.
 9. The downhole apparatus of claim 6, wherein the heating conduit extends axially through the steam generation chamber.
 10. An apparatus comprising: a heating conduit having a length dimension; a shell having a length dimension that extends over a length dimension of the heating tube, a width dimension, and opposing end walls sufficient to surround the heating conduit, the body disposed a distance from the heating conduit to define a volume between the heating conduit; a heating element disposed in a portion of heating conduit; and a thermally conductive material disposed in the heating conduit.
 11. The apparatus of claim 10, wherein the shell comprises a cylindrical body having a diameter as the width dimension and the heating conduit extends axially through the shell.
 12. The apparatus of claim 10, wherein one of the opposing ends of the shell comprises an inlet and the width dimension of the shell comprises a plurality of outlets.
 13. The apparatus of claim 10, wherein the heating conduit comprises a volume and the heating element is disposed in less than the entire volume, and the thermally conductive material in the heating conduit is present in amount that is less than the remaining volume.
 14. The apparatus of claim 10, wherein the thermally conductive material is a combination of the following substances: sodium peroxide; disodium oxide; silicon; diboron trioxide; titanium; copper oxide; cobalt oxide; beryllium oxide; dirhodium trioxide; trimanganese tetraoxide; and strontium carbonate.
 15. A method comprising: injecting steam from at least one steam generation chamber coupled to an oil recovery conduit into a reserve; and removing oil from the reserve through the conduit, wherein the least one steam generation chamber is disposed on the oil recovery conduit, and the steam generation chamber comprises a plurality of heating conduits each comprising a heating element and a thermally conductive material therein, and at least one reservoir surrounding the plurality of heating conduits from which the steam is produced.
 16. The method of claim 15, wherein the thermally conductive material is a combination of the following substances: sodium peroxide; disodium oxide; silicon; diboron trioxide; titanium; copper oxide; cobalt oxide; beryllium oxide; dirhodium trioxide; trimanganese tetraoxide; and strontium carbonate.
 17. The method of claim 15, further comprises producing steam in the at least one reservoir. 